The present invention relates to the field of perfumery. It provides in particular a new process for the preparation of 3a,6,6,9a-tetramethylperhydronaphtho[2,1.sub.-- b]furan, a compound of formula ##STR4## known in the art under the name of AMBROX. Owing to its olfactive characters of ambergris type and its power of diffusiveness, AMBROX has become over the years an essential ingredient in numerous perfume compositions of various nature.
Since its discovery [see Helv. Chim. Acta 33, 1251 (1950)], several syntheses have been proposed by different research groups. These are generally based on an oxidative degradation reaction of diterpene compounds such as (-)-sclareol or (+)-manool, or they use ambreine as starting material [G. Ohloff in Fragrance Chemistry, Ed. Ernst T. Theimer, P. 545, Academic Press (1982)]. This synthetic approach can be illustrated by means of the following reaction scheme: ##STR5##
Due to the fact that the above cited starting materials are of natural origin and that the yields for their extraction from the natural sources are small, it is necessary, in order to reduce the price, to dispose of an industrial manufacturing process which can offer improved yields.
The present invention provides a novel and original solution to the problem of preparing AMBROX.